It's hard to put a number on it. I think NSMBU + NSLU bundled with the system may be a bit of a problem too ... for some people that takes care of their immediate Mario fix, so maybe Mario 3D World is something they get 6-12 months later.

There's also probably a lot of parents that probably think NSMBU is the new Mario game ("it says "New" on the damn box!").

I think this is hurting 3D World.

3D Land had the benefit of being the only Mario platformer on the 3DS for quite some time.